Publication Title

UCLA Pacific Basin Law Journal



Document Type



This article compares the novelty standard under Japanese patent law with the novelty standard under American patent law. This article first explains the structure of the novelty and inventive step provisions under Japanese patent law and examines the interpretation and basic legal theories of these provisions. The inventive step standard developed out of the novelty standard. Thus, to understand the inventive step standard, it is necessary to understand the novelty standard.

Next, this article discusses the unique features of the Japanese novelty standard. The strict novelty requirements of the patent laws of the United States and European countries are contrasted with the relaxed substantial identity rule developed by Japanese courts, which will be discussed in detail. This article then evaluates the differences between Japanese and other novelty standards, and examines the reasons for those differences.

The final part of this article analyzes problems caused by the substantial identity rule and questions whether this rule is in fact necessary. The article concludes that the substantial identity rule should be abolished in Japanese patent law, and that the novelty and inventive step requirements should be clearly differentiated to harmonize the Japanese patentability standard with American and European standards, as well as to provide an objective patentability standard for the Japanese patent system.



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